Tool head and method for machining a metallic workpiece

Abstract

A tool head includes an ovoid basic element disposed about a center axis, at least two chip grooves formed in the basic element, and a number of major cutting edges. Each major cutting edge is disposed in a convex course along a respective chip groove of the at least two chip grooves. The major cutting edges define with their radially outermost region a nominal diameter. A radial distance from each major cutting edge to the center axis in a front, tip-side, arc portion increases up to the nominal diameter and in a rear, shank-side, arc portion decreases back down to a minimum diameter.

Description

BACKGROUND[0001]1. Field of the Invention[0002]Embodiments of the present invention relate to a tool head, in particular to a drilling head for machining a metallic workpiece, wherein the tool head has a center axis and at least two major cutting edges, which, viewed in a side view, take a convex course and define with their radially outermost region a nominal radius. Embodiments of the present invention further relate to a method for machining a metallic workpiece with a tool bearing such a tool head.[0003]2. Background Information[0004]In machine cutting, in particular in the drilling of hard materials, there is generally the problem of high load upon the cutting edges of the tool head. This usually has the result that only comparatively low machining rates can be set and / or a high level of wear occurs. The generated forces also occasionally lead under adverse conditions to chipping of the cutting edges.[0005]Such problems arise in particular, for instance, in the aviation sector,...

AI Technical Summary

Benefits of technology

[0011]Embodiments of the invention provide, among several benefits, a tool head which is improved with regard to the tool life and / or machining rate, in particular a drilling head for machining hard materials, in particular hard metals, such as titanium, or cast materials.

[0013]As a result of the distinct ovoid shape, the forces, in the machine cutting of a workpiece made of a hard material, in particular titanium, hard metal or cast material, are transmitted and conducted in a particularly advantageous manner along the ovoid surface of the drilling head, so that, all in all, a significantly lesser load upon the cutting edges is achieved. Studies have shown that, with an ovoid basic shape of this type, significantly higher cutting speeds and feed rates compared to traditional drilling tools can be obtained.

[0018]In addition, the rear arc portion is here expediently more strongly curved than the front arc portion. As a result, the axial length which is necessary in total is kept low, in combination with good force transmission.

[0020]Preferably, the individual arc portions are, in turn, preferably themselves composed of a multiplicity of individual segments having different radii. This enables, on the one hand, the advantageous and desired ovoid shape to be realized. At the same time, through a suitable choice of individual radii of the segments, an optimized force transmission is obtained, so that the cutting load is kept low overall. Expediently, the radii of the segments of the front arc portion here preferably steadily increase in the direction of the rear arc portion and, furthermore, the radii of the segments of the rear arc portion preferably steadily decrease again, starting from the front arc portion. In the region of nominal radius, the major cutting edge therefore has the greatest radius and thus the least curvature.

[0026]With the tool head which is described here, having the substantially ovoid basic shape, significantly higher cutting speeds compared to traditional tools can be obtained in respect of hard metals, in particular titanium. Thus the maximum cutting speed in the use of traditional drilling heads, for instance having normal conical grinding, is maximally VC=20 m / min. at a feed rate of F=0.05 mm / revolution. Studies have now shown that, with the tool head which is described here, the cutting speed was able to be doubled to VC=40 m / min., with the same or even improved drilling results, and the feed rate / revolution was likewise able to be significantly increased, for instance to values of F=0.12 to 0.15.

[0028]The particular advantage of the ovoid shape which is presented here is the diversion and transmission of the cutting forces and of the cutting pressure via the surface into the shank of the carrier, so that, all in all, the load upon the tool head is reduced.

Problems solved by technology

In machine cutting, in particular in the drilling of hard materials, there is generally the problem of high load upon the cutting edges of the tool head.

This usually has the result that only comparatively low machining rates can be set and / or a high level of wear occurs.

The generated forces also occasionally lead under adverse conditions to chipping of the cutting edges.

Such problems arise in particular, for instance, in the aviation sector, in which very hard metallic materials, for instance titanium, are used.

In the case of the material titanium, there is the particular problem that the chips tend to adhere or stick to the cutting edge.

Succeeding cuttings can then lead to a locally very high load upon the cutting edge, so that the risk of chipping is high.

Moreover, high loads also arise in respect of cast materials, for instance gray cast iron, in particular due to an inhomogeneous material structure.

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